We report transport, electromechanical, and structural properties of single core MgB₂/Fe wire produced using a new fabrication method, called designed internal Mg diffusion (IMD) process, which relies on the use of non-stoichiometric Mg + B pellets with excess Mg in place of a central Mg rod used in the standard IMD method. Structural analysis revealed the successful formation of a porous MgB₂ structure in the center and a dense circular MgB₂ layer surrounding this structure in the designed-IMD wire. Fast transport I–V measurements showed that the designed IMD method increased engineering critical current density (J _e) up to twice that of the IMD wires in self-field. The central porous MgB₂ structure shared the applied current and indirectly behaved as an internal stabilizer against quench damage at high applied currents.

Currently, MgB₂ wires made by the powder-in-tube (PIT) method are most often used in the construction and design of superconducting devices. In this work, we investigated the impact of heat treatment under both low and high isostatic pressures on the formation of a layered structure in PIT MgB₂ wires manufactured using the Mg coating method. The microstructure, chemical composition, and density of the obtained superconductive wires were investigated using scanning electron microscopy (SEM) with an energy-dispersive X-ray spectroscopy (EDS) analyzer and optical microscopy with Kameram CMOS software (version 2.11.5.6). Transport measurements of critical parameters were made by using the Physical Property Measurement System (PPMS) for 100 mA and 19 Hz in a perpendicular magnetic field. We observed that the Mg coating method can significantly reduce the reactions of B with the Fe sheath. Moreover, the shape, uniformity, and continuity of the layered structure (cracks, gaps) depend on the homogeneity of the B layer before the synthesis reaction. Additionally, the formation of a layered structure depends on the annealing temperature (for Mg in the liquid or solid-state), isostatic pressure, type of boron, and density of layer B before the synthesis reaction.